Appendix E - Geology and Soils Geotechnical Supporting Information COMBINED

LESTER-SHRINER PROPERTY 132-8-2 Page 8 conclude that the interpretation by Majmundar (1996) of a large landslide extending into the western portion of the Shriners parcel is incorrect. A more detailed description of the subsurface conditions is presented on the exploration logs in Appendix A. 3.4 GROUND WATER Free ground water was not encountered in the previous test pits (Lowney Associates, 1998) or in our recent explorations. Perched ground water adjacent to the existing creek will likely be encountered, particularly during the rainy season. Our recent reconnaissance and experience in the area indicates that seeps and springs may be encountered within cuts in the bedrock and in topographic swale areas. Fluctuations in ground water levels occur due to many factors including seasonal fluctuation, underground drainage patterns, regional fluctuations, and other factors. SECTION 4: GEOLOGIC HAZARDS 4.1 FAULT SURFACE RUPTURE As discussed above, several significant faults are located within 25 kilometers of the site. The site is not located within a State-designated Alquist-Priolo Earthquake Fault Zone. Our research, site reconnaissance, and limited field exploration has indicated no known surface traces of any Quaternary-active faults are thought to cross the site; therefore, fault surface rupture hazard is not a significant geologic hazard at the site. 4.2 ESTIMATED GROUND SHAKING Moderate to severe (design-level) earthquakes can cause strong ground shaking, which is the case for most sites within the Bay Area. A site modified peak ground acceleration (PGAM) was determined in accordance with Section 21.5 of ASCE 7-16. Therefore, we recommend a site- specific peak ground acceleration, PGAM, of 0.99g for this project. 4.3 LIQUEFACTION POTENTIAL The southern portion of the site flanking the existing creek channel is located within a State- designated Liquefaction Hazard Zone (CGS, Dublin Quadrangle, 2008). During strong seismic shaking, cyclically induced stresses can cause increased pore pressures within the soil matrix that can result in liquefaction triggering, soil softening due to shear stress loss, potentially significant ground deformation due to settlement within sandy liquefiable layers as pore pressures dissipate, and/or flow failures in sloping ground or where open faces are present (lateral spreading) (NCEER 1998). Limited field and laboratory data is available regarding ground deformation due to settlement; however, in clean sand layers settlement on the order of 2 to 3 percent of the liquefied layer thickness can occur. Soils most susceptible to liquefaction are loose, non-cohesive soils that are saturated and are bedded with poor drainage, such as sand and silt layers bedded with a cohesive cap. Ii! CORNERSTONE EARTH GROUP